Night Vision Imaging System (NVIS) applications often require displays to be compatible with Night Vision goggles. Long Visible and Near-infrared wavelength emissions cause displays to “bloom” or have a “halo effect”, which interferes with the user's goggles and also represents an undesirable beacon to other goggle users. Goggle interference is caused by the bright source/blooming object overloading the intensifier tube, which resultantly whites out adjacent features in the field of view or causes a loss of the entire image. Thus, radiance within NVIS-sensitive regions should be minimized or avoided, as shown in FIG. 1.
LCD display configurations typically include LED or fluorescent backlights. These backlights have the unwanted characteristic of emitting radiance in the NVIS region of the spectrum. This radiance causes blooming in the display which then must be minimized in NVIS applications.
NVIS compatibility is usually achieved using costly dichroic/thin-film and/or glass absorption based NVIS filters. The dichroic filter's spectral profile is controlled by vacuum deposition layered coatings to produce selective interference, such as a quarter wave stack. A glass absorption filter's spectrum is created by the absorption properties of the inorganic and/or organic compounds built into the glass substrate. Dichroic NVIS filtering schemes have spectrums that are dependent on incident angle transmission.
Moreover, both absorptive and dichroic NVIS filters often reduce a display's color gamut in the attempt to reduce NVIS radiance.
Accordingly, a need exists for an improved flat-panel display backlight which lowers the costs associated with typical NVIS solutions and avoids the emission of unwanted energies, while maintaining acceptable chromaticities. It is to the provision of solutions to this and other problems that the present invention is primarily directed.